Your body will experience an electric shock if current flows through it. The force that moves current is voltage. Voltage can be compared to elevation, where electrical current can be thought of as water in a river. Water will only flow down, or from a high point to a low point. If there is no elevation, the water in a river would not move. This is very similar to electrical current. It will not move if there is no voltage. If you provide a path for current to travel with voltage, current will take that path.
Show the class: The electric wire used in household wiring. If possible give a 15 cm (6 in) piece to everyone in the class and ask them to expose the three wires in the bundle.
Explain to the class: The outer shell is insulation. It keeps the inner three wires together and also protects us from electric shock. If the insulation is broken the wire is bad and should not be used.
If you examine the wires in any modern electrical appliance, you will find three wires. The red or black wire is called the "hot" wire, and power from the power source travels from this wire to the appliance. The white wire is called the "neutral" wire and provides a return path from the appliance to the power source. It is normally connected to the ground. The last wire (green) is a "ground" wire. It is an extra protection against shock, and normally attaches the rest of the appliance to the ground
You are almost always in contact with the ground, and for this reason if you touch the hot wire, you become part of an electrical circuit, and current will travel through your body to the ground. If you touch either of the other wires you will not receive a shock because the wires are at the same voltage as you (and thus there is no path for the current to travel). Lastly, if you touch the "hot" and "neutral" wire simultaneously regardless if you are touching the ground, you will receive a shock because you have completed a circuit, and there is a voltage across your body.
Electrical Equipment Checklist
Before using, inspect electrical tools and equipment for:
- damaged wires,
- broken connections,
- damaged plugs,
- missing prongs in the plug, and
- wet plugs.
Never use faulty equipment. It may cause injury due to electrical shock, fire or electrocution. A plug or electrical cord should not have exposed wiring. Exposed wires present a danger of electric shock or electrocution. Using an open front plug poses the risk of contact with live wires when plugging it to a electrical outlet. This also poses a risk of electric shock or electrocution.
Plugs and Cords
Electrical connections inside a tool will be broken if the power cord is pulled, twisted, or has sharp bends. Unplugging by pulling or jerking the power cord may break connections causing a short circuit, fire, or electric shock. Unplug power cords by holding the plug and pulling it out gently. Pulling the cord may cause a break in the wire resulting in a short circuit. Always switch off the power before plugging and unplugging a power cord. This practice will prevent sparks which may damage the plug and cause a fire.
Using long extension cords day after day may result in:
- a tripping hazard to other people in the area,
- an electrical hazard if the cord is damaged, and
- a fire hazard if the insulation is damaged by carts passing over the cord. Live and ground wires can come in contact (short circuit), causing a spark.
When you do maintenance work, cleaning, oiling or adjusting of a machine powered by electricity, you must lockout the power source. Follow procedures established by your school or company. When at work ask your supervisor for training regarding lockout procedures. Become familiar with the lockout procedures used by your school. It is essential that no one other than you can start the machine while you are working on it.
Lockout procedures have steps to ensure that you:
Do not touch or go near a downed power line wire. It may be live and carrying a current. In wet weather, you may get a shock even if you go close to the wire, even without touching the wire. Wet objects on the ground may act as electric conductors and bring you in contact with electricity.
Electrical emergencies can be caused by:
- Weather (lightning, ice storms, wind, etc.)
- Accidents (vehicle, machinery, workplace, etc.)
Basic Rules in the Event of an Electrical Emergency
- Notify the person in charge.
- Call 911 - follow their instructions.
- Never touch the victim unless you are sure that the power is off. A victim may be in contact with energized wires and you may be electrocuted if you come in contact with the victim.